Stick-form rigid adhesives of the type which are often slidably mounted in a reclosable tube for dispensing and which deposit a tacky film when rubbed onto a receiving surface, have become part of everyday life. Such adhesives are typically obtained from a water-soluble or water-dispersible adhesive-forming synthetic high polymer, particularly polyvinylpyrrolidone (PVP), dissolved or dispersed in an aqueous-organic liquid phase together with a compatible gel-forming component. The gelled composition can be shaped, e.g., formed and handled in stick form, and, if desired, disposed in an applicator such as a reclosable tube dispenser. When rubbed onto a receiving surface, the micelle structure of the gelled adhesive is destroyed and the solidified composition is converted into an adhesive paste.
Numerous attempts have been made to improve adhesive sticks of this type by modifying the gel-forming component and/or by modifying the solvent-activated adhesive-forming component.
Despite all those proposals, the oldest form of adhesive sticks, i.e., those based on soap gels such as described in U.S. Pat. No. 3,576,776 to Muszik, et al., which issued Apr. 27, 1971, remain by far the most widely used. In a particular popular embodiment of this technology, a solution of PVP in an aqueous-organic solvent mixture is converted into a soft-rubbing adhesive stick by an incorporation of alkali soaps of aliphatic carboxylic acids as the gelling agent, followed by gelling of the mixture.
These adhesive sticks, however, suffer from several disadvantages. For example, the application of the adhesive to the substrate material from these sticks is often not as easy as is desirable, with the result that rubbing the adhesive stick onto fragile substrates such as thin paper cannot be readily accomplished. Further, the adhesive layer formed frequently has an inconveniently short open time as compared to similar commercial products, losing tackiness rapidly and hampering careful alignment of the surfaces to be bonded.
Additionally, the glue sticks currently being used are colorless, thus making it difficult for the users to identify the area to which the adhesive has been applied. While the incorporation of a color dye or pigment into such adhesive sticks will aid in identifying those areas coated, the presence of colors in the adhesive markedly limits their use since the color may remain visible, particularly, if white or light colored substrates are employed. It would therefore be highly desirable to have an adhesive which is colored and readily identifiable when applied to a substrate, but which becomes colorless after application and drying. It would also be desirable to have an adhesive composition in stick-form containing additives which improve application characteristics.
Accordingly, one or more of the following objects will be achieved by the practice of this invention. It is an object of this invention to provide colored adhesive composition which upon application to a substrate becomes colorless. Another object of this invention is to provide an adhesive composition in stick-form containing additives which provide improved application characteristics.
A further object of the invention is to provide an adhesive composition containing polyvinylpyrrolidone.
Another object is to provide an adhesive composition containing a gel-forming component.
A further object is to provide an adhesive composition in stick-form.
A still further object is to provide a colored adhesive in stick-form which is disposed in a reclosable tube dispenser.
Another object of the invention is to provide a colored adhesive in stick-form which contains a colored indicator additive.
These and other objects will readily become apparent to those skilled in the art in light of the teachings herein set forth.